Different X apps in Wayland session start behave strange when Alt+Tab to them - mostly, mouse scroll doesn't work properly.
To make it work, Esc or any other key press is enough.
It seems Alt release event doesn't occur on Alt+Tab switch to XWayland windows.
Sample apps suffered: FF, Qt Creator.
STEPS TO REPRODUCE
switch with Alt+Tab from any Wayland window to FF X window and try to mouse scroll there
Scrolling doesn't work.
Instead, if browsing history is present for the tab, it will go back/forth by pages in the history on mouse wheel rotation.
Scrolling works as usual.
compiled from master
Created attachment 133813 [details]
Here is konsole run with WAYLAND_DEBUG=1 log and then switching to FF window, unsuccessful scroll there, then Esc and successful scroll after.
Created attachment 133814 [details]
A possibly relevant merge request was started @ https://invent.kde.org/plasma/kwayland-server/-/merge_requests/141
Git commit f67daa0711584058a8fefda76e898fe58d53ace7 by David Edmundson, on behalf of Andrey Butirsky.
Committed on 14/12/2020 at 17:09.
Pushed by davidedmundson into branch 'master'.
keyboard_interface: Always update modifiers cache
We send modifiers to the active client when they change, and when we
focus an existing client we send the cached state.
For this reason it's important we always update our internal store of
modifiers regardless of whether a surface is currently active.
Unit test is adopted accordingly.
M +7 -4 autotests/client/test_wayland_seat.cpp
M +5 -3 src/server/keyboard_interface.cpp